In 2006, he was one of 23 al-Qaeda figures who escaped from a Yemeni prison.

The group's deputy leader is believed to be Said Ali al-Shihri, a former prisoner at the United States' Guantanamo Bay detention facility, who was released from Saudi custody in 2007.

Abu al-Hareth Muhammad al-Oufi, another former Guantanamo detainee, has also been identified as a field commander for the group.

Experts say that al-Qaeda in the Arabian Peninsula comprises several hundred fighters. The group is said to have found sanctuaries among a number of Yemeni tribes, particularly in the eastern provinces.

'Strategic significance'

Analysts say Yemen is of huge significance to al-Qaeda.

"Weapons, training, crossing points and the launch of operations have all come from Yemen"

Abd Alelah-Haidar,analyst

"Weapons, training, crossing points and the launch of operations have all come from Yemen," Abd Alelah-Haidar, a "terrorism" specialist who has met Wuhaishi, told Al Jazeera.

"This country is seen as having strategic significance, not only by al-Qaeda, but also by others.

"[However,] their operations are not confined to the Arabian peninsula but also include Iraq, Afghanistan, Nahr al-Bared [in Lebanon], and Palestine."

Ali al-Ahmed, director of the Institute for Gulf Affairs based in Washington, said Yemen had become the third-largest haven for al-Qaeda, and the group there is perhaps the most stable when compared to units operating in Iraq, North Africa and South Asia.

"The one in Yemen now is really the most comfortable ... its probably the best funded," he told Al Jazeera.

"Its not the best trained [and] it doesn't have the best talent - that's why it hasn't been able to mount successful attacks. But it will come around in the coming years, and it will become a major threat."

Detroit claim

The al-Qaeda affiliate has claimed responsibility for an attempted attack on a US aircraft in Detroit on Christmas day, saying it was in response to raids in Yemen that it says were carried out by US jets, and had caused civilian deaths.

The Yemen-based al-Qaeda affiliate is saidto be one of the best funded [AFP]

The Yemeni government has said that it carried out military raids on December 17 and 24, saying more than 30 al-Qaeda members had been killed.

A New York Times newspaper report said Washington gave hardware, intelligence and other support to Yemeni forces for the raids.

"We tell the American people that since you support the leaders who kill our women and children ... we have come to slaughter you [and] will strike you with no previous [warning], our vengeance is near," a statement released by the group said.

"We call on all Muslims ... to throw out all unbelievers from the Arabian Peninsula by killing crusaders who work in embassies or elsewhere ... [in] a total war on all crusaders in the Peninsula of [Prophet] Muhammad."

The group has also claimed responsibility for attacks on the US embassy in Sanaa, the Yemeni capital.

US presence

Joseph Lieberman, chairman of the US senate homeland security committee, acknowledged on the "Fox News Sunday" television programme that the US has a "growing presence" in Yemen which included special operations, Green Beret special forces and intelligence.

Before the merger of the two Saudi Arabian and Yemen based groups, previous al-Qaeda incarnations had carried out a number of attacks across the region.

An emailed statement signed by Al-Qaeda in the Arabian Peninsula claimed responsibility for the 2004 attack on residential and office buildings in Khobar, Saudi Arabia whick left at least 22 people dead.

A suicide attack on an Aramco oil complex in Eastern Province in 2006 was also claimed by al-Qaeda.

In Yemen, seven Spanish tourists and their Yemeni guides were killed in a car bombing at an archaeological site in 2007.

Also an attack on the USS Cole warship in the harbour in Aden in 2000, which killed 17 US soldier, was carried out by al-Qaeda